From 3989a40825aeb12329f51781385b6a9e4aae06c2 Mon Sep 17 00:00:00 2001
From: silverpill <silverpill@firemail.cc>
Date: Thu, 16 Dec 2021 17:32:49 +0000
Subject: [PATCH] Send Undo(Announce) activity when repost is deleted

---
 src/activitypub/activity.rs        | 22 +++++++++++++++++++++-
 src/activitypub/receiver.rs        | 26 +++++++++++++++++++-------
 src/mastodon_api/statuses/views.rs | 27 ++++++++++++++++++++++++++-
 3 files changed, 66 insertions(+), 9 deletions(-)

diff --git a/src/activitypub/activity.rs b/src/activitypub/activity.rs
index 8e6cd36..ecc7d78 100644
--- a/src/activitypub/activity.rs
+++ b/src/activitypub/activity.rs
@@ -285,19 +285,39 @@ pub fn create_activity_announce(
     instance_url: &str,
     actor_profile: &DbActorProfile,
     post: &Post,
+    repost_id: &Uuid,
 ) -> Activity {
     let object_id = post.get_object_id(instance_url);
     let activity = create_activity(
         instance_url,
         &actor_profile.username,
         ANNOUNCE,
-        None,
+        Some(repost_id),
         object_id,
         vec![AP_PUBLIC.to_string()],
     );
     activity
 }
 
+pub fn create_activity_undo_announce(
+    instance_url: &str,
+    actor_profile: &DbActorProfile,
+    repost_id: &Uuid,
+) -> Activity {
+    let object_id = get_object_url(
+        instance_url,
+        repost_id,
+    );
+    create_activity(
+        instance_url,
+        &actor_profile.username,
+        UNDO,
+        None,
+        object_id,
+        vec![AP_PUBLIC.to_string()],
+    )
+}
+
 pub fn create_activity_delete_note(
     instance_url: &str,
     actor_profile: &DbActorProfile,
diff --git a/src/activitypub/receiver.rs b/src/activitypub/receiver.rs
index 6d182e2..68a744e 100644
--- a/src/activitypub/receiver.rs
+++ b/src/activitypub/receiver.rs
@@ -438,14 +438,26 @@ pub async fn receive_activity(
             unfollow(db_client, &source_profile.id, &target_profile.id).await?;
         },
         (UNDO, _) => {
-            // Undo(Like)
             let object_id = get_object_id(activity.object)?;
-            let reaction = get_reaction_by_activity_id(db_client, &object_id).await?;
-            delete_reaction(
-                db_client,
-                &reaction.author_id,
-                &reaction.post_id,
-            ).await?;
+            match get_reaction_by_activity_id(db_client, &object_id).await {
+                Ok(reaction) => {
+                    // Undo(Like)
+                    delete_reaction(
+                        db_client,
+                        &reaction.author_id,
+                        &reaction.post_id,
+                    ).await?;
+                },
+                Err(DatabaseError::NotFound(_)) => {
+                    // Undo(Announce)
+                    let post = get_post_by_object_id(db_client, &object_id).await?;
+                    match post.repost_of_id {
+                        Some(_) => delete_post(db_client, &post.id).await?,
+                        None => return Err(HttpError::NotFoundError("object")),
+                    };
+                },
+                Err(other_error) => return Err(other_error.into()),
+            };
         },
         (UPDATE, PERSON) => {
             let actor: Actor = serde_json::from_value(activity.object)
diff --git a/src/mastodon_api/statuses/views.rs b/src/mastodon_api/statuses/views.rs
index 37c9bd4..d8104bf 100644
--- a/src/mastodon_api/statuses/views.rs
+++ b/src/mastodon_api/statuses/views.rs
@@ -9,6 +9,7 @@ use crate::activitypub::activity::{
     create_activity_like,
     create_activity_undo_like,
     create_activity_announce,
+    create_activity_undo_announce,
     create_activity_delete_note,
 };
 use crate::activitypub::actor::Actor;
@@ -323,7 +324,7 @@ async fn reblog(
         repost_of_id: Some(status_id),
         ..Default::default()
     };
-    create_post(db_client, &current_user.id, repost_data).await?;
+    let repost = create_post(db_client, &current_user.id, repost_data).await?;
     let mut post = get_post_by_id(db_client, &status_id).await?;
     get_reposted_posts(db_client, vec![&mut post]).await?;
     get_actions_for_posts(db_client, &current_user.id, vec![&mut post]).await?;
@@ -333,6 +334,7 @@ async fn reblog(
         &config.instance_url(),
         &current_user.profile,
         &post,
+        &repost.id,
     );
     let mut recipients: Vec<Actor> = Vec::new();
     let followers = get_followers(db_client, &current_user.id).await?;
@@ -370,6 +372,29 @@ async fn unreblog(
     let mut post = get_post_by_id(db_client, &status_id).await?;
     get_reposted_posts(db_client, vec![&mut post]).await?;
     get_actions_for_posts(db_client, &current_user.id, vec![&mut post]).await?;
+
+    // Federate
+    let activity = create_activity_undo_announce(
+        &config.instance_url(),
+        &current_user.profile,
+        &repost_id,
+    );
+    let mut recipients: Vec<Actor> = Vec::new();
+    let followers = get_followers(db_client, &current_user.id).await?;
+    for follower in followers {
+        let maybe_remote_follower = follower.remote_actor()
+            .map_err(|_| HttpError::InternalError)?;
+        if let Some(remote_actor) = maybe_remote_follower {
+            recipients.push(remote_actor);
+        };
+    };
+    let maybe_remote_author = post.author.remote_actor()
+        .map_err(|_| HttpError::InternalError)?;
+    if let Some(remote_actor) = maybe_remote_author {
+        recipients.push(remote_actor);
+    };
+    deliver_activity(&config, &current_user, activity, recipients);
+
     let status = Status::from_post(post, &config.instance_url());
     Ok(HttpResponse::Ok().json(status))
 }